An environmental contractor can do this for you, or you can order a
mold test kit
online:

You just mail the cassette into the lab after leaving it exposed to the air, and they tell you what kinds of molds you have.

If the mold test comes back negative, but you've got odor or allergy problems, skip ahead to the allergen-control section.

To kill mold, you need to get the humidity below 50%, and around 35% is optimal.

If it's a mold problem in your basement, having a contractor
install vapor barriers around the outside of the foundation
of the house is probably the best long-term option.

(For an average size home, this can cost up to thousands.)

If a vapor barrier isn't an option (due to cost or because the
basement isn't a problem), then you can kill the mold by running a
dehumidifier.
A professional can install an expensive, high-throughput dehumidifier that can cover an entire house.

We opted to try out a
cheap Soleus portable, and it worked continuously for five years before breaking.

It kept our entire basement around 40%-45% humidity, effectively killing
the mold at an amortized cost of about $35/year.

Our model has three filters: one pre-filter cleaned by a vacuum once a
month, one HEPA filter replaced every three years and one
carbon
filter washed about every three months in a sink.

The difference for us was immediate.

We woke up with clear noses, clear heads and rested eyes the next day.

We were so impressed that we bought two more: one for our son's room,
and one for the basement.

Our son's eye and nose problems disappeared the morning after we
started running it in his room.

(It's quiet enough that the baby can
sleep with it on.)

We also got a good idea of which rooms in the house were the most polluted.

The clean-filter indicator came on for the Rabbit in our bedroom after
just two weeks (instead of 3 months), and when I pulled off the cover,
there was about a finger's-width of accumulated dust and pet hair on
the pre-filter, and thick coat on the HEPA filter underneath.

After that initial cleaning, it's since needed cleaning only every
couple months as recommended by the manufacturer.

We recommend this device to anyone with allergy problems.

Vacuums

To make matters worse, my wife and I love dogs.

So, for years, we've been trying high-end vacuum technology trying to
keep up with their shedding.